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[Licence| Download | New Version Template] adwg_v2_0.tar.gz(36 Kbytes)
Manuscript Title: Simulation of Ultra-High Energy Photon Propagation with PRESHOWER 2.0
Authors: P. Homola, R. Engel, A. Pysz, H. Wilczyński
Program title: PRESHOWER 2.0
Catalogue identifier: ADWG_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 184(2013)1468
Programming language: C, FORTRAN 77.
Computer: Intel-Pentium based PC.
Operating system: Linux or Unix.
RAM: < 100 kB
Keywords: Ultra-high energy cosmic rays, Extensive air showers, Geomagnetic cascading, Gamma conversion, PRESHOWER.
Classification: 1.1.

Does the new version supersede the previous version?: Yes

Nature of problem:
Simulation of a cascade of particles initiated by UHE photon in magnetic field.

Solution method:
The primary photon is tracked until its conversion into a e+e- pair. If conversion occurs each individual particle in the resultant preshower is checked for either bremsstrahlung radiation (electrons) or secondary gamma conversion (photons).

Reasons for new version:
  1. Slow and outdated algorithm in the old version (a significant speed up is possible);
  2. Extension of the program to allow simulations also for extraterrestrial magnetic field configurations (e.g. neutron stars) and very long path lengths.

Summary of revisions:
A veto algorithm was introduced in the gamma conversion and bremsstrahlung tracking procedures. The length of the tracking step is now variable along the track and depends on the probability of the process expected to occur. The new algorithm reduces significantly the number of tracking steps and speeds up the execution of the program. The geomagnetic field model has been updated to IGRF-11, allowing for interpolations up to the year 2015. Numerical Recipes procedures to calculate modified Bessel functions have been replaced with an open source CERN routine DBSKA.
One minor bug has been fixed.

Gamma conversion into particles other than an electron pair is not considered. Spatial structure of the cascade is neglected.

Additional comments:
The following routines are supplied in the package, IGRF [1, 2], DBSKA [3], ran2 [4]

Running time:
100 preshower events with primary energy 1020 eV require a 2.66 GHz CPU time of about 200 sec.; at the energy of 1021 eV, 600 sec.

[1] C. C. Finlay et al., Geophys. J. Int., 183, (2010), 1216, doi: 10.1111/j.1365-246X.2010.04804.x, http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html
[2] N. A. Tsyganenko, Institute and Department of Physics, Saint-Petersburg State University, Russia, private communication; http://geo.phys.spbu.ru/?tsyganenko/Geopack-2008.html
[3] http://wwwasdoc.web.cern.ch/wwwasdoc/shortwrupsdir/c341/top.html
[4] Numerical Recipes, http://www.nr.com